How can I simulate blocky smoke?
There is a way, but it's rather complicated and it's not based on the smoke simulation engine, therefore it's also inaccurate... But I'll show it anyway :) 



Create a particle system on your emitter

First of all, apply rotation and scale to your emitter (Ctrl+A), then add a particle system to it.

Particle systems, especially of the fluid type, are VERY sensible to their parameters, so you'll have to go through trial and errors by yourself. For an object the size of the default Monkey, these values work well (pay attention to the highlighted ones!):



If you need deflectors, use objects with Physics > Collision (give them some Damping, like 0.8).

Try the different parameters and play the animation until you're happy with how the smoke particle spread. At this point, bake the Particle Cache.

Create a cube for visualization

We won't render the particle system. Instead, we will use the density of the particles as an input for a volumetric cube.



The trick is all done in the cube material. It first divides the world in blocks; then it checks, for each block, the local density of particles. It uses this density information to choose the opacity of the volumetric shader.

Here are the nodes:



The blend file



Is for Blender 2.81. You won't be able to open it with 2.79. The instructions, however, should work well regardless.